                         \begin{tabular}{l*{1}{c}} \hline \hline \noalign{\smallskip}                                         & \multicolumn{7}{c}{\shortstack{World ranking}} \\                                         \cmidrule(l){2-8}                                           & \multicolumn{1}{c}{\shortstack{1--20}}                                          & \multicolumn{1}{c}{\shortstack{21--50}}                                         & \multicolumn{1}{c}{\shortstack{51--100}}                                         & \multicolumn{1}{c}{\shortstack{101--250}}                                         & \multicolumn{1}{c}{\shortstack{251--500}}                                          & \multicolumn{1}{c}{\shortstack{501--1000}}                                          & \multicolumn{1}{c}{\shortstack{1001--2000}} \\                 
\hline \noalign{\smallskip}
World rank: 1--20&    0.472\sym{***}\\
                &  (0.021)         \\
[1em]
World rank: 21--50&    0.341\sym{***}\\
                &  (0.024)         \\
[1em]
World rank: 51--100&    0.343\sym{***}\\
                &  (0.024)         \\
[1em]
World rank: 101--250&    0.266\sym{***}\\
                &  (0.011)         \\
[1em]
World rank: 251--500&    0.201\sym{***}\\
                &  (0.012)         \\
[1em]
World rank: 501--1000&    0.161\sym{***}\\
                &  (0.013)         \\
[1em]
World rank: 1001--2000&    0.106\sym{***}\\
                &  (0.017)         \\
\hline \noalign{\smallskip} 
N: Rank 1--20   &       19         \\
N: Rank 21--50  &       22         \\
N: Rank 51--100 &       38         \\
N: Rank 101--250&      103         \\
N: Rank 251--500&      154         \\
N: Rank 501--1000&      221         \\
N: Rank 1001--2000&      317         \\
N: Total        &     2873         \\
Adjusted R$^2$  &     0.16         \\
                         \hline \hline \noalign{\smallskip}                         \end{tabular}                 
